Object Organization - Hierarchies, collections, groups, empties?
I would suggest using collections for grouping objects together.  It's flexible, and very orginizable.

also, there is no reason for selecting a different shaped empty except for personal preference on shape, (or for selecting a shape that fits the object like you mentioned in the question.) 

and groups are now obsolete.  They were used in 2.79 and backwards.  Collections are the new and improved thing.